Television system



Jan. 9, 1940.

P. F. M. GLoEss 2,186,542

TELEVISION SYSTEM Filed Aug. l2, 1957 YE Fzg, I. 3-

yPatented Jan. 9,l

Nirso STATES PATENT OFFICE TELEVISION SYSTEM Paul Franois Marie Gloess,Paris, France, vassigner :to International `Standard ElectricCorporation, New York,y N. Y.`

Application August 12,1937, serial No. 158,662 In France September17,;19364 2 claims. Y (c1. 17e-#5.2)

The present invention relates to systems or apparatus for television andhas as one object the elimination oi certain drawbacks Which at presentexist particularly in scanning apparatus employing electronic means. l

It is known that in such apparatus frequencie lower than the framefrequency, and the socalled'D. C. component representing the meanbrightness of the image, are eliminated.

Thev present invention has, in particular, the

object of controlling the currents emitted by an electronic or similarscanning system, While taking into consideration one or more meancharacteristics of the scene'or image to be tele-z vised. This resultmay beattained by combining either with or inside the electronicscanning tube, a device sensitive to the mean characteristic of thescene to be televised which it is desired to keep under consideration,the currentproduced by this device being combined with the currentsproceeding from the electronic scanning device.

The invention is explained in more detail in the following descriptionbased onl the accomv panying drawing, in which:

Fig. l shows schematically an element of an electronic scanning system;

Fig. 2 shows schematically the electric circuit corresponding to 'anembodiment of the invenments such as l. A'The circuit of the mosaic*ele-V ment considered is completed by a polarising battery B and aresistance R at the terminals of which are collected the image signals.There falls on the cathode I a ray of light 3 proceeding from a point ofthe scene to be televised.

The reaction of the ray of light 3 on the cathode 2 produces, in thewell-known manner, an emission of photo-electrons. This emission ofphotoelectrons positively loads `the lcondenser C and thus produces aslowly Varying current inthe `resistance R. The same applies to all theelements of the mosaic and the corresponding currents are added yin theresistance R;

y denserC.l

Attire moment when the cathode scanning ray E passes over the element ofthe mosaic under consideration, it suddenly discharges the r condenser`C vand. the` correspondingdischarge current also passes throughv theresistanceR. The combination of these two currents practicallyeliminates the componentsof slow variations `of the discharge current ofthe elements of the mosaic, which current corresponds tothe meanillumination of the scene tobe televised. s The `embodimentshownschematically in Fig.

2 permits the complete imagesignal -to be reconstituted, that is to say,up to and including the zero frequency. lForthis purpose a photoelectriccell 5' is. employed,`having as far as possible, a characteristic ofsensitivity x similar or,

corresponding to that of the mosaic employed.

This ce1l'5 is associated with an optical system (not shown in Fig 2)adapted to receive in a given proportion the same total luminous ilux ofthe scene to be televised as that receivedby l the mosaic. This cell iilis then associated with'V the elements of the'mosacin the manner shown'in Fig. 2 that is to say, the cell 5v associated with ay polarisingbattery 6 is connected, on the one hand, over the battery 6,' to theanode.

2 and, on the other hand, to the common electrcdeforming one of. theYarmatures' of the con-- 1 The operation of the is thus as follows: Theauxiliary cell 5 produces in the resistance R currents of slow varia-Iunit shown 'in Fig. 2V

tion which are identical and of opposite direction to those produced bythe simultaneous charging of all the elements of the mosaic. In

this way the resistance R Willv no longer be travk ersed vexcept by thedischarge current of the elementary condenser `of the mosaic and thepotentials .collected on the terminals of R will thus represent solelythe image signals. It yWill also be noted that the devicedescribedpermits the direct component of this current also to be transmittedsince condenser C does not affect operation of cell 5.

Fig. 3-s`hows an embodiment of the invention in which the scene AB to betelevised is projected by means of an objective 6 on the mosaic 1 of acathode ray tube 8 provided with a deflector system yfor the scanningray shown in the form of a coil 9 which deilects the cathode rayl bymeans of the magnetic field which it produces. It is clear thatothertypes of deector systems may also be employed.v l

A second objective I0 projects an image of the same scene on a Window IlWhosedimensions,

may be adjusted in accordance with the portion of the scene which it isdesired to televise.

Behind this adjustable window Il is an optical condenser I2concentrating the luminous bundle which has passed through the Window IIon a photo-electric cell I3 similar to the cell 5 shown in Fig. 2. Thecell I3 is associated with the Various elements of the mosaicy inaccordance with the manner shown in the caseY of the cell 5 on Fig. 2,The connection of the cell to the elements of the mosaic l and theresistance R has also not been shown in Fig. 3 in order not tocomplicate this drawing.

The dimensions of the opening of the window II and the position, of thisopening may be adjusted either automatically or by manual control. Fig.3 shows,-by way of. example, a manual control of the opening of thewindow by means of an operating knob I4, this control being combinedwith the means for controlling of the amplitude of the sweep of thecathode ray. This window or diaphragm Ii is composed of .two V-shapedelements, I5 and it. These two elements are connected 4to eachother by means of pins I9, sliding in slots, such as Il and E8. Thesepins are movable along the diagonal of the'gure formed by the twobranches 45 and I6, which, in the example under consideration, is in theform of a square, and may also slide in a slide, such as Z5, whichpermits the device to present to the objective I@ an opening which`remains square, its dimensions thus being adapted to be varied asdesired. The adjustment of the screen may be made in the following'mannerz-a spring 2G presses against the element I5 thereby forcing theelem-ent i5 to assume ,a particular position byA virtue of `theconstruction of the device previously described. The connection betweenthe mechanical device and the manual control M is effected by means of acable El connected to the element I6, passing over a pulley, such as 22,and

winding on a drum 23. vThis drum may ber mounted, for example,- directlyon the axle of the adjusting knob ld and stops (not shown) may beprovided in order to maintain the diaphragm at a particular opening.

On this same axle is mounted a potentiometer 2li which permits thedeflection of thev cathode scanning ray to be adjusted, for example,bythe, v

currents passing through the deiiecting coils only one of which, 9, isshown in Fig. 3. This adjustment is performed so that the portion of themosaic 'I scanned by the cathode ray corresponds to the size of theopening of the window II and, consequently, to the chosen portion of thescene to be televised.

The arrangement shown in Fig. 3 permits the applic-ation of theinvention even in the case in which the amplitude or deflection of thescanning ray is caused to vary, particularly in order to obtain sceniceffects on the screen of the receiver.

The invention which has been described in its application to televisionmay also be employed for similarapplioations such as, for example, infacsimile transmission systems.

The invention is obviously not limited to the embodiments describedwhich may undergo numerous modifications without departing from thelimitsy of the invention, thus instead of a singlev additionalphoto-electric cell, several may be provided.

Although the embodiment described only serves to take into considerationthe mean illumination of the scene or image to be televised, it is clearthat the invention is not limited to this particular case and that, forexa ple, for the transmission of television in colourseveralcompensating photo-electric cells, such as ti, might be employed, forexample one cell for each fundamental colour ef the image.

What is claimed is:

l. A television transmitting system comprising an electronic scanningphoto-electric `device for scanning an image of a eld of View, anauxiliary photo-electric device responsive to the average light value ofsaid fieldv of view, an adjustable Window in front of said auxiliarydevice icr dening the area kof the field of View which is projected uponsaid auxiliary device, and means for simultaneously adjusting theaperture area of said window and the amplitude of sweep of the cathoderay of said photo-electric device rst mentioned.

2. A color ltelevision system wherein a separate transmittingarrangement according to claim l is utilized for each fundamental colorto be transmitted.

PAUL FRANCOIS D/IARIE GLOESS.

